The present disclosure relates to a light-transmitting film including continuously aligned three-dimensional structures on one of the surfaces, a method of forming the light-transmitting film, and a liquid crystal display.
Liquid crystal displays (LCDs) consume less electric power and can be formed small and thin compared with cathode ray tubes (CRTs). Recently, liquid crystal displays of various sizes are put to use, such as small devices including mobile phones, digital cameras, personal digital assistants (PDAs) and large devices including liquid crystal televisions.
Liquid crystal displays are divided into transmissive types and reflective types. A transmissive liquid crystal display includes a liquid crystal display panel formed by sandwiching a liquid crystal layer with a pair of transparent substrates, first and second polarizers disposed on the light incident side and the light emission side, respectively, of the liquid crystal display panel, and a backlight unit that functions as an illumination light source. The backlight unit may be a direct light type in which a light source is disposed directly below the liquid crystal display panel or an edge light type that uses a light-guiding plate.
To collect the light emission direction of light from the light source to front side, a configuration is known in which a light-transmitting film known as a luminance improvement film is interposed between the backlight unit and the liquid crystal display panel (for example, refer to Japanese Patent No. 3158555). The luminance improvement film is made of a prism sheet having prisms with triangular cross-sections periodically aligned at a fine pitch on a first side and collects light by vertically emitting the light from the backlight to the front side.
However, since with a known prism sheet, the index of refraction is isotropic and the light emitted from the prism sheet is usually not polarized, about half of the light emitted from the prism sheet is absorbed by the first polarizer disposed on the light incident side of the liquid crystal display panel. Consequently, there is a problem in that the illumination light from the backlight cannot be used efficiently and luminance cannot be improved.
By interposing a reflective polarizer that transmits a first linearly polarized component and reflects a second linearly polarized component between the prism sheet and the liquid crystal display panel, light efficiency of the backlight can be increased and the luminance can be improved.
However, by using such a reflective polarizer, the production cost of the liquid crystal display apparatus increases and the number of components increases. Thus, it becomes difficult to reduce and size and thickness of the apparatus. Moreover, even when a reflective polarizer is used, the function is not necessarily sufficient in that, for example, part of the polarized component in the absorption axis direction of the first polarizer leaks.